drm/edid: drop extra local var

We don't need override as a variable for anything.

Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/4d249173b34758e1d6c4a74eb98518d180f0a8ae.1649685475.git.jani.nikula@intel.com